Apparatuses for measuring characteristics of cotton fibers are known, which are provided with a preparation device for preparing the sample of fibers to be tested, wherein the sample picked up is in the form of a “beard”. In these known apparatuses, the preparation device for preparing the sample comprises a pair of plates that face one another, are parallel and movable relatively to one another; one of these two plates is perforated and arranged at a lower height with respect to the other that, on the other hand, is coupled to actuator means towards and away from the other.
Below the perforated plate a comb is arranged, which is guided in a movable manner in both senses along at least one translation direction.
A mass of cotton fibers is interposed between the two plates and pressed between them so that protuberances of fibers project from the holes of the lower plate. The comb is made to slide below the perforated plate so that its teeth meet the protuberances of fibers projecting therefrom in order to grip tufts of fibers from them. The tufts of fibers gripped by the comb are then carded and brushed, respectively by a card and by a brush, in order to eliminate excess fibers not properly anchored to the teeth of the comb from them and to parallelize the fibers “hooked/fastened” to the teeth of the comb forming a sample of fibers in the form of a “beard”, i.e. in which the fibers are substantially coplanar and parallel to one other.
The comb supporting the “beard” of fibers thus sampled introduces the latter into measuring devices for measuring their characteristics like, for example, devices for measuring the length and/or the dynamometric characteristics (i.e. elongation and resistance at break by tension).